Among electric drive devices used in an electric power steering device, there are drive devices which have two groups of motor coils and inverter circuits, which can be driven independently. Consequently, even if there is an abnormality in the motor coil and inverter circuit of one group, driving of the motor can still be continued by the other normally functioning group.
Among conventional electric drive devices of this kind, there is a device wherein, if there is a shorting fault in a switching element of the inverter circuit in the control unit, severe effects on the braking torque due to the fault are suppressed by increasing the motor drive output in the normal group (see, for example, PTL 1).
Furthermore, in a further electric drive device, if the switching element suffers an open fault, then even a group where an abnormality has occurred operates continuously in the phases in which continuous operation is possible, and the output in the normal phases is increased by an amount corresponding to the decrease in torque in the phase where the abnormality has occurred (see, for example, PTL 2).
Moreover, in a further electric drive device, if one motor of a plurality of motors suffers a fault, the decrease in torque in the motor suffering an abnormality is compensated for by raising the current limit value of the normally functioning motor (see, for example, PTL 3).